1. Field of the Invention
This invention relates to conduit supporting structure and more particularly to a combination locking strip and support member for securing one or more cables to a longitudinally extending channel-shaped support structure in a manner permitting the cable to be secured in a selective position along the length of the support structure.
2. Description of the Prior Art
It is well known to use interlocking clamp plates in suspending electrical cable, pipes, conduits and the like from a channel-shaped support structure. Generally the clamp plates are curved to form a seat for the cable. The clamp plates are notched at one end to form a shoulder engageable with the flanges of the channel structure and the opposite ends of the plates are bolted together so as to securely grip the cables. Examples of this type of cable hanger are disclosed in U.S. Pat. Nos. 3,145,962; 3,486,726; 3,522,921; 3,547,385; 3,650,499; and 4,417,711.
The recognized disadvantage of the above described cable hanger is that the clamp plates are connected by threaded members and the like which are subject to damage when exposed to a corrosive environment. Corrosive damage to the metallic clamp plates and the threaded connection of a bolt to the plates can prevent effective reuse of the conduit hanger and substantially weaken the structural strength of the clamp plates. Also, if the threaded connection of the bolt to the plates becomes so corroded that it freezes the connection, movement of the cable hanger on the channel-shaped support structure for selective positioning of the cable can be substantially prevented.
U.S. Pat. Nos. 3,226,069; 3,532,311; and 4,119,285 represent other metallic clamping elements to be used in conjunction with a channel structure which could be similarly subjected to weaken the structure or prevent its future selective positioning within the channel structure. Additional, the clamping elements shown therein would appear to be even less adaptable for accommodating cables of different sizes than would the types of clamp plates described hereinabove. U.S. Pat. No. 3,266,069 employs overlapping metal bands which can be adjusted but are difficult to initially install and properly size around a cable. U.S. Pat. No. 3,532,311 appears to be preformed for accommodating a particular size cable. Additionally, U.S. Pat. No. 4,119,285 includes a pair of clamp jaws which are presized to resiliently support a limited range of cable sizes therein.
As an alternative to the metallic clamping plates for securing cables to a channel structure, it is known to use flexible stainless-steel bands to secure cables, such as pipes or conduits, to a channel structure as illustrated in U.S. Pat. No. 3,633,859. One of the primary advantages of this type of cable connecting device is the use of flexible bands which are not subject to corrosion but are adjustable to accommodate a plurality of cables. U.S. Pat. No. 4,379,537 appears to employ metal bonding straps on a cable hanger which is not associated with a channel structure. Although the straps may be subject to corrosion, they can at least be adjusted for different sizes or numbers of cables. U.S. Pat. No. 3,677,339 discloses a tube bank arrangement in which a plurality of tube coils is connected to a spacer bar by U-shaped tube clips which are retained in grooves of the spacer bar. Locking strips engage the tongues of the tube clips to retain the coils in the tube clips and secure them to the spacer bar.
It is also well known to utilize nylon cable ties for securing together a plurality of cables, wires, hoses and the like. The nylon cable ties are particularly adaptable in corrosive environments because they are chemically resistant to solvents, alkalies, acids, oils and greases. U.S. Pat. No. 3,632,070 discloses such a nylon cable tie used in conjunction with a right-angled mounting bracket for supporting a plurality of cables.
Another device that is commercially available for gathering and directing single or groups of cables is a plastic cable holder having a gate for facilitating cable entry and preventing unintentional cable exit. The cable holder is adaptable for connection to a mounting panel. However, the above described cable ties and cable holders are not readily adaptable alone for securing cables and the like to a channel-shaped structure.
On the other hand, there are two prior art support members which are of interest and are capable of being utilized in conjunction with a longitudinally extending channel-shaped support structure. The particular type of structure which both employ could be defined to include a pair of spaced side walls having free end portions turned inwardly to form opposed, longitudinally extending flanges. The support member for U.S. Pat. No. 3,651,546 is referred to as an elongated fastening element. The elongated fastening element in one embodiment disclosed therein is constructed of a tubular metal portion having depending support walls with a slot therethrough for receipt of a pipe hanger strap or similar device. The tubular metal portion surrounds a resilient body and includes in each side wall thereof slots extending inwardly from each of its opposite ends. The resilient body extends beyond the base of these slots to be aligned with a major portion of each of the slots. Accordingly, to install the first embodiment of U.S. Pat. No. 3,651,546, the upper half of the tubular metal portion is inserted between the flanges of the support structure and rotated to align the end slots thereof with the flanges. As the flanges extend into the slots, the resilient body is deformed to provide biasing against the inner edges of the flanges. In another embodiment, the resilient body extends outwardly from an end of the upper portion of the tubular metal portion. Similar insertion and rotation results in the resilient body creating frictional contact on the side walls of the support structure after the flanges are again aligned with end slots in the tubular metal portion. Accordingly, whether creating frictional contact on the edges of the flanges or on the interior surfaces of the side walls, the embodiments of U.S. Pat. No. 3,651,546 includes one means for insuring that the elongated fastening element when properly positioned within the support structure, will tend to remain in position but will be capable of selective longitudinal movement along the support structure. However, the elongated fastening element is composed of two different materials, one of which is metal and subject to corrosion in the same manner as described hereinabove for other prior art devices, and includes the depending support walls. The support walls would receive the pipe hanger strap or device in a location spaced from the support structure to significantly add to the overall height or thickness of the combined cable and support structure configuration when the pipe or cable is secured thereto.
The other support member which is of interest is described as a framing channel cable clamp and is old by Thomas and Betts Company. The framing channel cable clamp is made of a resiliently deformable, noncorrosive material and includes structure which is again intended to cause it to be resiliently positioned between the flanges for selective longitudinal positioning along the support structure. However, rather than creating biasing against the side walls or the edges of the flanges of the support structure, the framing channel cable clamp appears to include a pair of opposed, resilient wing elements at each flange with one wing element exterior of the support structure and one wing element interior of the support structure. The wing elements are adapted to create opposing frictional contact on the exterior surface and interior surface of each of the flanges. Consequently, since a portion of the framing channel cable clamp extends outwardly of the support structure in overlying relationship to the flanges, a cable or cables secured to the support structure would not be in direct contact with the support structure to slightly add to the overall height or thickness of the combined cable and support structure configuration. More significant than the minor increase in overall height or thickness is the arrangement utilized in the framing channel cable clamp for installing a cable tie therein and the lack of accessability to the opposite ends of the cable tie for properly securing a cable to the support structure. The framing channel cable clamp includes a single slot in an interior portion thereof which loosely receives a cable tie and allows it to lie longitudinally within the interior of the support structure. In other words, if the framing channel cable clamp were to be utilized in a vertically extending support structure, the cable tie might inadvertently freely slide out of the slot. If it were oriented the other way in the slot, the free end could slide completely into the slot so that the end of the tie having the locking slot would be positioned against the slot to the clamp. On the other hand, even if the support structure were to extend horizontally so that the cable tie would not slide into or out of the slot, the slot configuration of the framing channel cable clamp can present problems. Nylon cable ties typically used to secure cables are flexible but tend to have sufficient resilience to cause them to remain relatively straight until the ends are joined to form a loop. Consequently, with the tie loosely received within the slot, the ends thereof might lie naturally within the interior of the support structure to complicate retrival and to make it more difficult to quickly join the ends around a cable. Accordingly, although the framing channel cable clamp appears to be capable of being selectively positioned longitudinally within the support structure and to maintain that position when a cable is to be secured thereto, the cable tie to be utilized to secure the cable is not held in any particular position or orientation for simple insertion of the cable between the ends thereof. Finally, because the framing channel cable clamp employs the preformed, opposed wing configuration, it is adapted to be installed between flanges of a particular size and shape to prevent it from being utilizied on other support structures having a similar configuration but different flanges.
Therefore, there is a need for a cable support member that is resistant to damage in a corrosive environment and sufficiently adaptable for securing cables and the like to a channel-shaped support structure where the support member is easily assembled and disassembled for alignment of the cable against the support structure and adjustable for selective positioning of the cables longitudinally on the channel-shaped support structure.